1. Field of the Invention
The present invention relates to a battery pack and a detection method, more specifically, to a secondary battery pack including, for example, a lithium-ion secondary battery and a detection method executed by the secondary battery pack.
2. Description of the Related Art
In recent years, along with prevalence of portable electronic apparatuses such as a laptop PC (Personal Computer), a cellular phone, and a PDA (Personal Digital Assistance), lithium-ion secondary batteries having advantages of a high voltage, a high energy density, and light weight are widely used as power sources.
A battery pack accommodating a battery cell constituted of such a secondary battery is provided with a protection circuit for prohibiting charge and discharge when an anomaly in the battery cell is detected. Specifically, for example, a voltage, a charge-discharge current, a temperature, and the like of the battery cell is measured every time a predetermined time passes to thus detect an anomaly such as overcharge, over discharge, and overcurrent with respect to the secondary battery based on a result of the measurement. Then, when any of the anomalies as described above is detected, control is performed to turn off a charge-discharge switch for controlling charge and discharge or prohibit charge and discharge with respect to the secondary battery by fusing a temperature fuse.
Moreover, the battery cell deteriorates due to a repetition of the charge and discharge, and a battery capacity is thus reduced. In addition, when the battery cell is used for over a long period of time such as about several years, the battery cell may become unusable. In such a case, the battery cell may need to be replaced for restoring the battery capacity of the battery cell to a level equal to or higher than a level of a new battery cell.
When the battery cell is replaced improperly, a newly-replaced battery cell and the battery cell originally accommodated in the battery pack may differ in characteristics. Since a control specification of the protection circuit is determined in accordance with characteristics of the original battery cell, when the battery cell is replaced improperly, there is fear that an anomaly of the battery pack cannot be detected to thus result in an inconvenience of the battery pack. Therefore, the replacement of a battery cell is normally conducted on a manufacturer side. A user is prohibited from opening a battery pack and improperly replacing a battery cell.
For example, Japanese Patent Application Laid-open No. 2005-353518 (hereinafter, referred to as Patent Document 1) discloses a battery pack that is capable of recognizing an alteration history of opening a battery pack and replacing a battery cell.